Perchlorate is an emerging inorganic contaminant, at least in the United States. It has been reported that perchlorate is present at detectable concentrations in public drinking water supplies affecting more than 11 million people in the United States. Both natural and anthropogenic origins are contributing sources of perchlorate in the environment. Through the intake of perchlorate-containing food or water, perchlorate ions can be transported to the thyroid gland and cause adverse effects on the metabolism and production of thyroid hormones. The National Academy of Science has recommended a perchlorate reference dose (RfD) of 0.7 μg/kg-day. Perchlorate is already regulated in California and Massachusetts drinking water with the maximum contaminant level (MCL) of 6 and 2 μg/L, respectively. In February 2011, the U.S. EPA expressed the government's intent to establish a national primary drinking water regulation (NPDWR) for perchlorate. Therefore, methods that are effective in eliminating perchlorate from water are needed.
Due to the highly soluble, non-volatile and kinetically inert nature of perchlorate ion in water, the elimination of perchlorate from contaminated water is a challenging task. Many efforts have been made to develop efficient techniques for the removal of perchlorate from water. Among the various chemical and physical processes, granular activated carbon (GAC) and ion exchange resins have received much attention as methods for perchlorate removal. Although adsorption processes can be effective for the removal of perchlorate at trace concentrations in water, such processes require regeneration of the adsorbents or ultimate disposal of perchlorate-laden spent adsorbent materials. Furthermore, competitive and inhibitory adsorption of other anions against perchlorate can be a technology barrier for such adsorption processes. Membrane technologies such as ultrafiltration (UF) and nanofiltration (NF) have also been used to remove perchlorate from water. However, the lack of selectivity and the use of chemicals (polymers) make such methods unattractive. It would therefore be desirable to develop additional, improved methods for removing perchlorate from water.